1. Field of the Invention
The present invention relates to a disc-medium playback method and apparatus, and more particularly, to a disc-medium playback method and apparatus that do not repeatedly play back the same musical piece even when the musical piece is recorded in both a two-channel format and a multichannel format.
2. Description of the Related Art
In general, DVD-audio discs are played back by the following three methods:
In a first method, content such as audio titles (ATTs) is divided into groups, and each group is recorded in a two-channel format and a multichannel, for example, six-channel, format in program chains (PGCs). When a DVD player is set for two-channel playback, the group is played back by using a two-channel playback PGC in a PGC block. When the DVD player is set for six-channel playback, the group is played back by using a six-channel playback PGC.
In a second method, content such as ATTs is divided into groups, and each group is recorded in a six-channel format together with a downmix coefficient that represents downmixing from six channels into two channel. When a six-channel DVD player is provided, it plays back the six-channel group. When a two-channel DVD player is provided, it plays back the six-channel group after downmixing into two-channel format.
In a third method, content such as ATTs is divided into groups, and each group is played back.
Japanese Unexamined Patent Application Publication No. 11-250629 suggests a data structure including audio content which has cells for defining an audio title (ATT) playback unit, and whose playback sequence is determined by defining the playback sequence of the cells.
The problem of the same musical piece being repeatedly played back does not occur in the above first and second methods, but occurs in the third method. For example, when Group 1 is provided for a two-channel format and Group 2 is provided for a multichannel format, Group 1 and Group 2 frequently contain the same musical piece. In such cases, when all the groups are played back in group number sequence, as before, each musical piece is played back twice. In a disc changer that normally plays back a disc through and then starts playback of the next disc, a disc change operation is performed after each musical piece is played back twice.
FIGS. 11A and 11B show the problem of the conventional art. A first group Gr#1 is a two-channel group, and a second group Gr#2 is a six-channel group. A third group Gr#3 is a PGC block, and includes a two-channel PGC PGC#1 and a six-channel PGC PGC#2. A fourth group Gr#4 is a downmix (DM) block that is downmixable from six channels to two channels. During playback in an AOP (audio only player) mode, playback is sequentially performed from the first track Trk#1 in the first group Gr#1. When all the tracks in the first group Gr#1 have been played back, the next group Gr#2 is then played back. Therefore, in a case in which a disc having the groups shown in FIG. 11A is played back by a two-channel DVD player, playback is performed in the order shown in FIG. 11B, that is, Gr#1 (2ch)-Gr#2(6ch)-Gr#3 (PGC#1)-Gr#4 (DM). For this reason, the two-channel group Gr#1 and the six-channel group Gr#2 include the same musical piece, and the musical piece is played back twice.
The art disclosed in the above publication cannot overcome such a problem of the same musical piece being played back twice.